In November Centrica warned the cap would cost it £70m in lost operating profits in the first quarter of 2019.

This was after British Gas shed 372,000 household accounts in the four months to the end of October as customers left its SVT.

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Centrica says that Ofgem had not properly taken into account the wholesale energy costs that “all suppliers incur” when it devised the cap.

Explaining its decision to seek a judicial review, it said: “Through this action Centrica has no intention to delay implementation of the cap, and does not expect the cap to be deferred in any way.

“As we have previously said, we do not believe that a price cap will benefit customers but we want to ensure that there is a transparent and rigorous regulatory process to deliver a price cap that allows suppliers, as a minimum, to continue to operate to meet the requirements of all customers.”

Ofgem told the BBC that it “carried out an extensive consultation process when setting the price cap and we believe that it offers consumers on poor value tariffs a fairer deal.

“In the event of a judicial review we would defend our proposals robustly.”

The regulator says the new energy price cap could save 11 million customers an average of £76 a year on their gas and electricity bills.

But it has already said that the level of the cap is likely to rise in April 2019, to reflect the higher cost of wholesale energy. As a result, the average annual saving in 2019 is likely to be lower.